WARSAW: Arsonists attacked a mosque in Poland Wednesday during the Muslim Eid al-Adha holiday amid tensions over a nationwide ban on halal animal slaughter and protests by animal rights activists.

"It was definitely arson," Grazyna Wawryniuk, spokeswoman for regional prosecuters in the Baltic port city of Gdansk where the mosque is located, told AFP.

"We have launched an investigation to determine the motives and identify the perpetrators," she said.

The fire damaged a door and part of the mosque's interior, she said. The imam for Gdansk, Hani Hraish, told local media the attack in the early hours of Wednesday was a very rare act of violence in his community.

"Yesterday we celebrated Eid here normally. It was beautiful, joyous, we had a huge crowd and we didn't notice anything strange," he said.

"It's very unpleasant for us, very harmful. The fire didn't just burn our mosque but our heart and souls too," he added.

Poland's small Muslim and Jewish communities have come under pressure this Eid holiday to respect a January 1 ban on ritual halal and kosher slaughter after the Constitutional Court deemed it incompatible with animal rights legislation.